Nonslip fabrics and method of preparation thereof



Patented Dec. 13, 1949 NONSLIP FABRICS AND METHOD OF PREPARATION THEREOFAlden D. Nate, Stamford, Conn., assignor to a corporation of MaineAmerican Cyanamid Company, New York, N. 1.,

No 1mm. Application October 4,1944, Serial No. 551,233

6 Claims. (Cl. 117-138.

This invention relates to the stabilization of woven or knitted fabricsto prevent slippage of one thread or fiber over another, and is directedparticularly to fabrics composed of or containing synthetic fibershaving a hard and smooth surface wherein thread slippage is aparticularly serious problem. The invention will be described andillustrated with reference to fabrics composedof or containing nylonthreads, which normally have hard and smooth surfaces that cause themtoslip readily, but it should be understood that the principles of theinvention are applicable to fabrics composed-of or containing othersynthetic fibers having similar characteristics.

Considerable difliculty has heretofore been experienced with woven andknitted fabrics composed Of or containing hard synthetic fibers of thetype of nylon threads because of the ease with which the threads willslip out of place when the fabric is pulled or rubbed. This is mostnoticeable in the slippage of the warp threads over the filling threadsin woven fabrics. It is particularly troublesome in marquisette insectnetting and screen cloth of the types that are now used by the armedforces in the South Pacific and other tropical and semi-tropical areas.Nettings and screens composed of synthetic fibers such as nylon having ahard finish are preferred over cotton and other natural fibers forservice in these areas, but the meshes of the nettings are readilyenlarged by thread slippage to the point where insects can easilypenetrate the screen. It is a principal object of the present inventionto pro-' adverse service conditions.

Another important field of application of the principles of theinvention is in preventing runs in knitted fabrics, such as nylonstockings. When fiber slippage is prevented in fabrics of this class thebreaking of a single thread is not so likely to cause a run or "ladder"as is the case in ordinary nylon stockings, since the threads aresecurely fastened to each other at their points of intersection.

I have found that slippage of hard and smoothsurfaced threads of thetype of nylon is effectively prevented to a remarkable degree when thefabric contains a cured alkylated methylol melamine, which functions tobind the fibers together and thus to stabilize the fabric. I have foundthat this class of materials has unique properties as a binding orstabilizing agent for hard synthetic fibers of the type ofnylon threa s.and for this purpose it gives results that are far superior to thoseobtained with ureaformaldehyde resins, thermoplastic resins, and othertypes of binding agents. Accordingly, my invention in its broadest formconsists in the application to fabrics of the class described of analkylated methylol melamine resin under conditions such that the threadsof the fabric become coated and/or impregnated with the resin in itscured and water-insoluble condition. The production of treated fabricscontaining the cured resin in quantities such as to prevent slippage ofthe threads constitutes a further object of my invention, and isincluded within the scope thereof.

Alkyl-ated or alcohol-reacted methylol melamines are resin-formingmaterials obtained by reacting methylol melamines with aliphatic primarymonohydric or polyhydric alcohols in the presence of small quantities ofacidic catalysts. It is generally understood that the reaction takesplace between the alcohol and one or more methylol groups of themethylol melamine with the elimination of water and the formation of anether, and therefore the final products are proper- 1y designated asalkylated methylol melamines. The term alcohol-reacted methylolmelamines, of course, defines the same materials in terms of theirmethod of manufacture. This class of materials has previously beenapplied to wool and cotton fabrics to prevent shrinkage therein, butthey have never previously been applied to nylon and similar fabrics forthe purpose of fiber stabilization.

Although a wide variety of alkylated methylol melamines is available foruse in practicing my invention, I have found that the best results areobtained when the water-soluble type of alkylated methylol melamine isemployed. It is a known fact that water-insoluble alkylated methylolmelamines can be prepared by reacting almost any aliphatic primarymonohydric alcohol with a methylol melamine containing from 2-6 methylolgroups in the presence of an acid catalyst such as hydrochloric acid,and these products have been used in the preparation of lacquer surfacecoatings. However a class of water-soluble alkylated methylol melamineshas recently been developed by carrying out the same type ofcondensation under carefully controlled conditions, using a loweraliphatic monohydric alcohol such as methyl or ethyl alcohol or a lowerpolyhydric alcohol such as ethylene glycol or di-ethylene glycol. Thelatter class of resin-forming materials is greatly superior for thepurposes of the acorns present invention since it avoids unduestiflening of thewoven fabrics when applied in the amounts necessarytoobtain satisfactory stabilization. Moreover, the water-solublealkylated methylol melamines and particularly the water-solublemethylated methylol melamines are much more eifectlve in preventingslippage of one fiber over another than are the correspondingwater-insol-.

uble resins. and therefore the water-soluble variety constitutes thepreferred class of materials used in practicing m invention.

The exact quantity of resin which will produce optimum results will varywith the type. of fabric and with the degree of slipp e prevention thatmay be desired. In general, I have found that amounts of about 3% f theresin, based on the dry weight of the fabric, are sufficient with verylight fabrics to produce an appreciable and-inmany cases a. satisfactorystabilization, whereas quantities of more than 20% are usuallyunnecessary. I have obtained very satisfactory results using about 6 to10% of water-soluble methylated methylol melamine, based on the dryweight of the cloth, and therefore this may be taken as the preferredquantities for use in practicing my invention. The resin is preferablyapplied in the form of a relatively dilute aqueous solution.con-

taining about 8 to 20% of the resin together with a a curing acceleratorto assist in curing or polymerizing the resin to its insoluble conditionafter tts application to the fabric. Ordinarily about 0.35% of a mixtureof equal parts of diammonium hydrogen phosphate and hexamethylenetetramine, based on the weight of the resin, is used for this purpose.

The water-soluble methylated methylol melamine which I employ isprepared by reacting a substantially monomeric methylol melamine withmethanol under slightly acid conditions with careful temperaturecontrol. The following procedure has been used with success in preparingthis resin:

1 mol of melamine is mixed with 3.3 mols of aqueous 37% formaldehydepreviously adjusted to a pH of approximately 8.0, the temperature beingraised to 70 C. and maintained at this point until a clear solution isobtained. The solution is then immediately cooled and allowed to set andthe mass is broken into small pieces. and dried by circulating warm airat a temperature not exceeding 55' C.

The resulting dried powder is added to twice its weight of 95% methanolcontaining 0.5% l of oxalic acid crystals, based on the. weight of themethylol melamine. The mixture is heated to 70 C. and held at thistemperature for approximately minutes, or until a clear solution isobtained, whereupon it is immediately neutralized by the addition ofsufllcient sodium hydroxide solution to raise the pH to approximately9.0. The neutralized reaction mixture is then evaporated to 80% solidsunder reduced pressure so that the emperature does not rise' above 50 C.

It should be understood that the invention is not limited to the ratiosof formaldehyde, melamine and methanol described in the foregoingexample. 0n the contrary, from 2 to 6 mols of formaldehyde may becombined with each mol of melamine, and the resulting methylol melaminemay be reacted with from 2 to 6 mols of methanol. The term water-solublemethylated methylol melamine therefore describes any water-solubleproduct prepared by reacting methanol with a substantially monomericmeth- 1s 8. A method of stabilizing marquisette fab- '4ylolmelaminecontainingztoemolsofoombined formaldehyde under conditionssuch that I a water-soluble reaction product is formed.

In addition to the advantages enumerated above, it is a furtherimportant feature of my invention that it can be applied to grey clothor as it comes from the loom. One advantage of applying the resin to thecloth at this stage of ment to stabilize the fabric.

The fabrics to be stabilized may be impregnated with the resin solutionby any suitable procedure such as those now in commercial use.Preferably the process is applied by running the fabric through theresin-containing liquor in a 2 or a 3 bowl mangle, which is usually mmin tandem with a tenter frame for drying the fabric to the proper width.The mangle bowls are preferably rubber, but may be of any conventionaldesign. After drying, the fabric is heat-cured by any of the usualmethods, such as by running it through a loop dryer for 3 to 5 minutesat 300 1''. Following this treatment the fabric may be given a shortwash in a dilute solution of soap and sodimn carbonate. if desired,although the washing is not necessary and is frequently omitted in thetreatment of some types of fabric.

As a specific example the following is cited: 15,000 yards of nylonmarquisette insect netting as it came from the loom, without scouring,

were treated by the process of my invention. The treating bath was madeup by dissolving 140 lbs. of methylated methylol melamine, prepared asdescribed above, together with 4 lbs. of the above-described curingaccelerator in gals. of warm water and adding pigment colors to producethe desired shade. The pickup at the mangle was approximately 30%, andtherefore the fabric contained 4% of the methylated methylol melamineresin. The impregnated fabric was passed through a loop drier at 300'F., using a drying time of approximately 4 minutes, after which it wasfound that slippage between the warp and filling threads was effectivelyprevented even after three rayon launderings. Attempt to displace thefiling threads in the treated and cured fabrics by pulling them with thefingers were unsuccessful, whereas the unstabilized fabrics were readilydistorted by this treatment.

What I claim is:

l. A method of stabilizing woven net fabrics composed of hard-finishnylon threads which comprises impregnating said fabrics with an aqueoussolution of about 13-20% of their weight of a water-soluble alkylatedmethylol melamine in an uncured condition, and subsequently heating theimpregnated fabrics to convert the impregnating agent into a curedresinous binder.

2. A method of stabilizing woven 'net fabrics composed of hard-finishnylon threads which comprises impregnating said net fabrics with anaqueous solution of about 3-20% of their weight of a water-solublemethylated methylol melamine in an uncured condition, and subsequentlyheating the impregnated fabrics to convert the impregnating agent into acured. resinous binder.

rics composed of hard-finish nylon threads which comprises impregnatingsaid fabrics with an aqueous solution of about 6-10% of their weight ofa water-soluble alkylated methylol melamine in an uncured condition, andsubsequently heating the impregnated fabrics to convert the impregnatingagent into a cured, resinous binder.

4. A method of stabilizing marquisette fabrics composed ofhard-finishnylon threads which comprises impregnating said fabrics with an aqueoussolution of about 6-10% of their weight of a water-soluble methylatedmethylol melamine in an uncured condition, and .subsequently heating theimpregnated fabrics to convert the impregnating agent into a curedresinous binder. I

5. A woven net fabric composed of nylon threads, said fabric beingstabilized against thread slippage by a content of about 3-20% of itsweight of a cured alkylated methylol melamine resin, said resin havingbeen applied uniformly to the fabric as an aqueous solution ofREFERENCES CITED The following references are of record in the file ofthis patent;

UNITED STATES PATENTS Number Name Date 2,329,622 Johnstone Sept. 14,1943 2,340,359 Young Feb. 1; 1944 2,343,039 Smith Feb. :29, 19442,343,093 Smith Feb. 29, 1944 2,370,362 -'Light Feb. 27, 1945

